Method of forming a core yarn



Jan. 12, 1965 w. K. DONALDSON ETAL METHOD oF FORMING A CORE YARN I5 Sheets-Sheet 1 Filed March 11, 1965 Jan- 12, 1965 w. K. DONALDSON ETAL. 3,164,951

METHOD oF FORMING A CORE: YARN Filed March 1l, 1963 3 Sheets-Sheet 2 venlor By Y Atorneys Jarl- 12, 1965 w. K. DONALDSON ETAL 3,164,951

METHOD 0F FORMING A CORE YARN Filed March l1, 1965 :5 Sheets-Sheet 3 United States Patent() 3,164,951 Marrron or nona/uno A conn YARN William Il. Donaldson, Cheadle, and lan Eddleston,v

Yarns made from asbestos fibres tend not to be very strong, and in order to produce stronger yarns so-called core spinning may be used. In core spinning a single core consisting of a continuous thread of high strength such as a metal wire, cotton yarn or synthetic fibre filament, is introduced in the spinning process to provide a strong central core around which a thread of staple fibres is twisted to constitute the yarn. However, in such reinforced yarns, the staple fibres tend to skin back, that is to say, the covering of the staple fibres slips on the core and the yarn ceases to be uniform over its length. The continuity of the outer covering of fibres may in fact be broken, thus exposing the core.

When two or more such single-cored yarns are doubled the fibre covering of the cores can no longer skin back to any substantial extent. However, the production of such a composite yarn tends to be expensive, since it requires an extra process, namely that of doubling. Moreover, each thread of the staple fibres is itself made by carding the fibres to form a sliver and twisting the sliver. Although Skinning back is substantially eliminated in the resultant yarn, it is often difficult to prevent skinning back during the doubling process when the core is of a smooth material such as glass or metal.

Various proposals have been made to produce cornposite yarns of asbestos and glass, since for many purposes the properties of asbestos and glass are complementary. In attempting to produce a satisfactory composite yarn of asbestos and glass without doubling two such yarns we have found that the elimination of Skinning back presents an extremely diflicult problem. The same problem arises if the glass is replaced by any other smooth continuous filament, e.g. a metal wire or a continuous thread of nylon or a polyester. After experiments extending over several years we have now solved this problem.

Yarns according to our invention are composed of slivers of staple asbestos fibres and smooth continuous filaments. The term Lcontinuous filament when applied to glass means a glass thread of indenite length, usually of the conventional multi-filament type, commonly consisting of 204 monosfilaments. When applied to nylon or polyester it means a thread of indefinite length composed of one or more monofilaments and presenting a smooth surface, as distinguished from the rough surface presented by the so-called bulk yarns. When applied to metal the term continuous filament means a very thin wire, say of 38 S.W.G., of, for instance, brass, copper, Zinc or stainless steel. All these continuous filaments have strength and smooth surfaces so that asbestos tends to skin back over them. None of them has any inherent stretchability.

Asbestos slivers are produced by carding and may or may not have some twist in them. As is well known, they do not always consist solely of asbestos but quite often consist of asbestos fibres mixed with rayon or cotton fibres, though the asbestos always predominates by weight.

The essence of the invention is that an asbestos sliver is sandwiched between continuous filaments, there being at least one continuous filament on each face of the sliver, and the length of each of these filaments in any given length of the yarn being identical with that of each of the others. VThe resultant sandwich is twisted.

the filaments over the surfaces of the rollers.

Patented Jan. 12, 1965 ice The invention is particularly applicable to the production of asbes-tos-glass yarns, and normally there are only two continuous glass filaments.

In carrying out the invention the sandwich .may pass through a roller nip to a device by which the twisting is effected, and the identical lengths of filaments are delivered to the nipl under'tension from a rotary cylinder. This may be part of a capstan device or a wound package of the filaments.

The invention will be described Vin more detail with reference to the accompanying drawings, in which:

FIGURE 1 is a diagrammatic cross-section through two continuous glass filaments and an asbestos sliver;

FIGURE 2 is a cross-section through these components after twisting into yarn;

FIGURE 3 shows diagrammatically one form of apparatus used in producing the yarn; v

FIGURE ll is a section similar to FIGURE l showin three continuous filaments and one sliver; and

FIGURE 12 is another similar section showing three continuous filaments and two slivers.

The most simple form o-f yarn according to the invention is produced from two continuous glass filaments 1 and 1 between which an asbestos sliver 2 is sandwiched in the way diagrammatically shown in FIGURE l, the resultant sandwich then being twisted into the cross-sectional shape diagrammatically illustrated in FIGURE 2. The sliver 2 is used in the flattened form illustrated in FIGURE l, in which it has two opposite wider sides forming faces and two narrow' sides.

Referring now to FIGURE 3 the two filaments 1, wound into packages 3 on bobbin tubes 4, are drawn off by over-end unwinding and passed through guides S and round fixed rods 6 so that some drag to their further onward movement is set up. Next both pass round a cap stan device 7 on the kind well known in the textile industry and'comprising a pair of rollers 8 and 9. Each filament is looped two or more times round both rollers, there being so many such loops as to prevent any slip of In practice three or four turns of glass filaments are enough for this purpose. Then in each revolution of the roller 9 a length of each filament equal to the length of the circumference of the roller 9 is fed forwards. In the device 7 shown both the rollers are freely rotatable.

The filaments 1 and 1 are next taken through a guide 10, which is firmly held in a clamp 11; This guide has three U-shaped eyes 12, 13 and 14, one above another, and theV filaments 1 and 1 pass through thetop and bottom eyes 12 and 14. The asbestos sliver 2 is unwound from a flanged bobbin 15, which is vertically guided by guides (not shown) and engages and rests on a positively driven drum 16, so that the sliver is unwound at a rate equal to the peripheral speed of the drum 16. The sliver 2 passes through the central eye 13 of the guide 10. As

` nip between two rollers 17 and 18, being guided just be lost.

fore entering the nip' by a guide 19, which is supported by the same clamp 11 as the guide 1). This guide 19, and its position in relation to the rollers 17 and 18, are important factors in obtaining good results. In the passage between the rollers 17 and 18 there is very considerable risk of one filament being pushed round the edge of the asbestos sliver to come to lie on the same face of the sliver as the other filament or of the sliver being pushed laterally out of face contact with both filaments. To avoid this there must be no risk of either filament wandering in its passage from the capstan device 7 to the rollers 17 and 18, and both must be under tension throughout the Whole of this travel. As they enter the nip between'the rollers 17 and 13, the two filaments 1 and 1 should make a fairly wide angle with one another, for example an angle of 30, since if at this moment they are running nearly parallel to one another they are found to push the asbestos sideways so that the desired face contact is lost. If the tension in the filaments in their travel from the guide 19 to the nip between the rollers 17 and 18 is too low, then the asbestos tends to push the filaments sideways, and again the desired face contact is At this stage the asbestos itself can be under very little tension, say a total tension of grams, but each of the glass filaments must be under much greater tension, e.g. a tension of 100 grams. It is essentially for this reason that the friction device c-onstituted by the rods 6 is provided.

The guide 19 has three V-shaped eyes 2t), 21 and 22. The filament 1 passes through the eye 20, the sliver through the eye 21, and the filament 1 through the eye 22, in each case with change of direction in so doing. This change of direction can be clearly seen in FIGURE 4, which also shows the approach of the two filaments 1 and 1' to the roller at an angle of about 30.

From the nip between the rollers 17 and 18 the sandwich assembly passes to a twisting device, shown in FIG- URE 3 as a conventional flyer 23 serving to twist and wind the assembly on to a bobbin 24, the fiyer and bobbin both being positively driven, the bobbin at a faster speed than the flyer.

Because the assembly passes through the nip between the rollers 17 and 18 there is no risk of the twist put into it running back beyond this nip. These rollers may be replaced by any other device which will likewise stop the twist from running back, e.g. a bar round which the assembly is pulled under tension.

The rollers 17 and 18 positively move the sandwich forward. The surface speed of the roller 1S is made the same as that of the drum 16 by interconnecting their driving shafts as shown diagrammatically by lines and gears 26, and the drives to the fiyer 23 and bobbin 24 are similarly connected as shown diagrammatically by lines 27 and gearing 28.

In the guide 19 the two filaments and the sliver are kept apart from one another. This is not necessary, since one filament and the sliver can pass through the same eye, and if this is done the guide may then become diamondshaped as shown at 29 in FIGURE 7. The guide may even become circular, provided that all three components must change direction in passing through it and are under tension so that each will tend to take the shortest path and therefore become accurately centered in passing through the guide. This requirement may necessitate the replacement of the guide 10 by one which will ensure the necessary change in direction of the three components in passing through the guide 29.

The capstan device 7 may be replaced by a package of equal lengths of the two filaments, since such a package when rotated will unwind identical lengths of the filaments. The production of such a package is diagrammatically shown in FIGURE 8, two filaments 1 and 1 being unwound by over-end unwinding to pass round rods 6 and enter a traversing eye 30 from which they are wound into a package 31 round a bobbin tube 32. Since the two filaments are wound under substantially equal tension as a result of passing round the rods 6, identical lengths are wound into the package. The wound package 31 is put on a spindle 33 shown in FIGURE 9, and is unwound from this against the action of a brake 34. The remainder of the apparatus shown in FIGURE 9 is the same as that in FIGURE 3, and the provision of the brake 34 ensures that the filaments 1 and 1 pass to the guide 1t) under tension.

Another form of device for ensuring that identical lengths of the two filaments are delivered to make contact with the sliver is a capstan with one roller driven and the other idle. This is shown at 35 in FIGURE 10, the driven roller being shown at 36 and the idle roller at 37. Such a capstan may be used when the twisting is to be effected by ring spinning, or by a flyer frame with one of the elements (the fiyer or the bobbin) idling. It will be appreciated that such a capstan positively feeds forward equal lengths of the two filaments. It must not only do this, but also feed both at a rate appropriate to the degree of twist required. The sandwich passes from the nip between the rollers 17 and 18 to an eye and thence to a traveller 39 of a ring-spinning frame, from which the twisted sandwich is wound on a spindle 40. As diagrammatically illustrated in FIGURE 10, the driven roller 36 of the capstan device 35, the drum 16 and the ring spindle 40 are synchronised in their rates of rotation.

A package such as that shown at 31 may also be used in ring spinning, but in such a case need not be positively braked; rather it should unwind on to a device such as the positively driven capstan 35 shown in FIGURE 10.

An idling capstan such as that shown at 7 may be replaced by a rotary tension pulley. In such a pulley, instead of the conventional V-shaped groove around its circumference the sides of the V are provided with teeth which intersect at the base of the V and make the threads take up a zig-zag path around the circumference of the pulley, thus preventing them from slipping and ensuring that they travel at the same rate.

We find that to produce a yarn of maximum strength but with minimum snarl any initial twist in each filament should be in the opposite direction to that of the final twist of the yarn. Thus if the final yarn has an S-twist, the filaments 1 and 1', if twisted at all, should have Z-twist.

FIGURE 11 shows the use of three filaments, two filaments 1 in contact with one face of the sliver 2 and the other filament 1 in contact with the opposite face. The advantage of this is that if, despite all the precautions described above, there should be a tendency for lateral movement of the filaments in relation to the sliver, the desired sandwich of sliver between filaments is still likely to be produced and twisted.

A heavier yarn may be made by so-ealled gang spinning from three filaments 1, 1 and 1" and two slivers 2 and 2 sandwiched together as shown in FIGURE l2.

A further modification consists in replacing any one or each of the single continuous filaments referred to by more than one filament running parallel and side by side at all times and exactly equal in length to one another.

For some purposes a yarn externally surrounded by a helical winding of a metal wire is required. Such a wire may be fed to the twisting device with the other elements of the yarn, and although it is a smooth continuous filament it need not be present in the lengths required in the continuous filaments which with the asbestos sliver form the sandwich of the invention.

Yarns made according to the invention are several times stronger than an equivalent asbestos yarn devoid of continuous filaments. They have uniform strength throughout their length, whereas normal asbestos yarn varies considerably in strength. Indeed the strength of a yarn according to the invention is essentially that of the continuous filaments, and because they are of identical length they will take any applied tension substantially equally. if the filaments wereV not to be of exactly the same length, then one would take more tension than the other, and brealr first, Whereafter the other would break. The proportion by weight of asbestos to glass may be varied widely, depending upon the nature of the product desired. Thus, it may be desired to produce a yarn of highV strength which is to be bonded to a plastic material and in such a case the asbestos .may serve to give the yarn a rougher surface in order to improve adhesion between the yarn and the plastic in addition to which it may` improve the mechanical properties of the finished product, the impact strength for example. Alternatively, a relatively low proportion of glass to asbestos may be used with the object of strengthening what would otherwise be rather a weak yarn. We have found that by combining about 12% of glass threads (by weight) with an asbestos sliver in accordance with the invention, the strength of the yarn produced is about three times greater than that of a simple asbestos yarn.

We claim:

1. A method of producing a yarn which comprises drawing a sliver of staple asbestos bers having two opposite flat faces and at least two smooth continuous lilaments of equal extensibility from' sources of supply to la sandwiching point, the filaments being drawn at equal speeds, at such point bringing one of said filaments into Contact with one flat face of said sliver and another of said filaments into contact with the other at face `of said sliver to sandwich theilaments'and the sliver, maintaining an equal substantial tension on each of said filaments between the source of supply thereof and the sandwiching point, twisting the sandwiched product, and preventing the twist from passing backward beyond the sandwiching point.

2. A method as claimed in claim 1 in which the lilaments are of glass.

3. A method of producing a yarn which comprises drawing a sliver of staple asbestos fibres having two opposite at faces and at least two smooth continuous filaments of equal extensibility from sources of supply to a sandwiching point, the filaments beingdrav/n at equal speeds, at such point bringing one of said filaments into contact with one dat face of said sliver and another of said filaments into contact with the other flat face of said sliver to sandwich the iilaments and the sliver, maintaining an equal substantial tension'on each of said laments between the source of supply thereof and the sandwiching point, twisting the sandwiched product, and pressing at least one of the filaments against a smooth surface at the sandwiching pointA with the sliver overlying it so as to prevent the twist from passing backward beyond the sandwiching point.

4. kin a method as claimed in claim 1, maintaining a substantially lower tension on the sliver from its source of supply up to the sandwiching point than on the laments. Y

5. A method of producing a yarn which comprises.

feeding from sources of supply to the bite of a pair of positively driven rolls a sliver of staple asbestos fibres having opposite fiat faces with such faces facing the two rolls, feeding to the bite of the rolls, between each roll and each flat face of the sliver a smooth continuous fila-` ment so as to form between the rolls a sandwich having on each face of the sliver a filament in engagement with the sliver face and lying between such face and the roll,

References Cited by the Examiner UNITED STATES `PATENTS 1,439,166 12/22 Heany 57m-160 1,458,577 6/23 Heany s- 57-144 X 1,732,593 10/29 Cannon 57-144 2,217,049 10/40 Greenleaf a 57--144` 2,311,356 2/43 Astley 57--144 $02,820 9/59 Bronson et al 57-140 3,068,636 12/62 Masurel 57-140 MERVIN STEN, Primary Examiner. 

3. A METHOD OF PRODUCING A YARN WHICH COMPRISES DRAWING A SILVER OF STAPLE ASBESTORS FIBERS HAVING TWO OPPOSITE FLAT FACES AND AT LEAST TWO SMOOTH CONTINUOUS FILTAMENTS OF EQUAL EXTENSIBILITY FROM S OURCES OF SUPPLY TO A SANDWICHED POINT, THE FILAMENTS BEING DRAWN AT EQUAL SPEEDS, AT SUCH POINT BRINGING ONE OF SAID FILAMENTS INTO CONTACT WITH ONE FLAT FACE OF SAID SLIVER AND ANOTHER OF SAID FILAMENTS INTO CONTACT WITH THE OTHER FLAT FACE OF SAID SLIVER TO SANDWICH THE FILAMENTS AND THE SILVER, MAINTAINING AN EQUAL SUBSTANTIAL TENSION ON EACH OF SAID FILAMENTS BETWEEN THE SOURCE OF SUPPLY THEREOF AND THE SAND WICHING POINT,TWISTING THE SANDWICHED PRODUCT, AND PRESSING AT LEAST ONE OF THE FILAMENTS AGAINST A SMOOTH SURFACE AT THE SANDWICHING POINT WITH THE SILVER OVERLYING IT SO AS TO PREVENT THE TWIST FROM PASSING BACKWARD BEYOND THE SANDWICHING POINT. 